In the opening decade of the 2lst century, there again are major challenges for the field of Infectious Diseases because of five major developments: 1) an epidemic of immunocompromised hosts in whom antimicrobial chemotherapy is less effective; 2) widespread development of resistant microbes; 3) emergence of new pathogens; 4) re-emergence of old pathogens thought to be vanquished; and 5) the potential of dealing with the challenges of biological warfare. The net result is a new and major threat to the health of the world population. An adequate response to the existing problems will require a multidisciplinary effort from basic scientists, clinicians, government, and industry. This application requests funds for renewal of a training program at the Albert Einstein College of Medicine for the training of new scientists at the predoctoral and postdoctoral levels to help meet this challenge. We have assembled a dynamic group of investigators, all of whom have research projects supported by the National Institutes of Health and other prestigious funding organizations. We have developed a rigorous program for training, which emphasizes both formal learning in the classroom and goal-oriented research at the laboratory bench. The various participating laboratories, which have been augmented by the recruitment of three new faculty, provide an unusually broad program for training, which includes projects in host defense mechanisms and in molecular mechanisms of virulence in viruses, bacteria, parasites and fungi.